Adjusting AFM Constants for larger injectors

[dmcl]

looking to see if anyone else might have anything to add on this or maybe has tried some similar stuff that i havent tried yet..

anyway, the way i understand that u are supposed to adjust the AFM constants for larger injectors is to drop all of the values in the AFM constants map by the same amount (-30 from all values across the AFM constants map for 19lb injectors ive been told). i did just that to a performance bin (hakentt's performance 91+ octane bin FWIW) which seemed to have much improved my cold starting and general running with my 19lb injectors (previously on stock AFM constants and overfuelling). now i dont have my wideband yet so i cant check/compare AFR's but it seems to have done the trick at any rate.. will check when my wideband arrives.

so... having the laptop in the car and just getting out of work i decided to play with tunerpro in the car. i took a notion to mess around with the AFM constants and drive the car a bit. i used tunerpro RT's data tracing and noticed that under heavier throttle the hits were all coming from the latter half of the AFM constants map (after it jumps up higher on the graph/in values). so i got to thinking and i felt like dropping all of the AFM constants by 30 seemed to water down the performance a little.. i want to say even WOT but i dont know if AFM constants are factored into the equation once the ECU goes into WOT mode or not.

so the upshot is i ended up increasing the last 4 parts of the AFM constants map back to their normal value (for stock injectors, i added the 30 back on that i took off) but i left the first 4 parts as i had them (-30, for 19lb injectors) and i swear i can feel a difference.. it seems like the car pulls better under heavy throttle and possibly even WOT but still runs great at part throttle and lower loads thanks to the first 4 parts of the AFM constants map being adjusted down for the 19lb injectors. seems like the extra fuel from the 19lb injectors is making a benefit under high load and possibly WOT.

has anyone tried doing this? adjusting the first 4 parts and last 4 parts seperately from one another? what did u find/notice if u did?

[dmcl]

tried this on a different performance map and it seemed to run better with all 8 of the AFM constants dropped by 30 instead of just the first 4. just got my wideband today so that should take the guess work out of all of this. maybe AFR's were a little lean up top on that other map and thats why it felt like it was stronger with the last 4 AFM constants not reduced by 30 for the 19lb injectors i have?

[e30rott]

Could you PM me the constants you're using? I under you said -30 from hakentt's 91+ octane bin, I just don't have that specific bin so I'm not sure if I'm in the ball park or not.

[dmcl]

its universal.. all M20 maps have (or should have unless modified for injectors of M30 AFM already) the same values for the AFM constants.

have been messing with my own map for a while now and have dome alot of little tweaks for my own personal setup. it was running rich on the 19lb injectors even with the AFM constants all dropped by 30. i leaned out the WOT fuel maps as necessary starting from where i was having problems with acceleration breaking up and the engine stuttering from being too rich. without looking at the map its been leaned out the most around the last 1/3 of the WOT fuel maps tho i did also lean off the first 2/3 just not by nearly as much. my fuel maps actually start off close to normal but the higher up the revs u go the more the values drop and its still a little on the rich side up top lol

car goes like stink compared to running the same performance tune wit hthe stock AFM and adjusted for the injectors prior to modifying it for the MAF. i had a solid AFR reading of about 12-12.5 before installing the MAF, after the map it was rich across the board but moreso in the higher revs. even running rich the difference was crazy.

[revlimit]

did anybody try adjusting the map injector constant, they are 3 values of 128, on my newest XDF?

[dmcl]

i did on another map but think i only tried it once so not really had enough time to check it out.

once i get everything i want transferred to a bigger maps file i will be dropping injector constants to around 97-100 for 19lb injectors.